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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

BODIPY and dipyrrin as unexpected robust anchoring groups on TiO 2 nanoparticles

Covalent attachment of molecules to metal oxide surfaces typically demands the presence of an anchoring group that in turn requires synthetic steps to introduce. BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) chromophores have long been used in dye-sensitized solar cells, but carboxylic acid groups typically had to be installed to act as surface anchors. We now find that even without the introduction of such anchors, the unmodified BODIPY can bind to TiO 2 surfaces via its BF 2 group through boron–oxygen surface bonds. Dipyrrin, the parent molecule of BODIPY, is also capable of binding directly to TiO 2 surfaces, likely through its chelating nitrogen atoms. These binding modes prove to be even more robust than that of an installed carboxylate and offer a new way to attach molecular complexes to surfaces for (photo)catalytic applications since, once bound, we show that surface bound BODIPY and dipyrrin derivatives exhibit ultrafast photoinjection of electrons into the conduction band of TiO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Accurately constituting robust interfaces for high-performance high-energy lithium metal batteries

High-energy lithium metal batteries (LMBs) have received ever-increasing interest. Among them, coupling lithium metal (Li) with nickel-rich material, LiNi x Mn y Co z O 2 (NMCs, x ≥ 0.6, x + y + z = 1), is promising because Li anodes enable an extremely high capacity (∼3860 mA h g −1 ) and the lowest redox potential (−3.04 V vs. standard hydrogen electrode), while NMCs can achieve a much higher capacity of ∼200 mA h g −1 and lower cost than those of LiCoO 2 . However, the resultant Li‖NMC cells have been hindered from commercialization due to a series of challenges related to the interface stability of both Li anodes and NMC cathodes. Specifically, Li anodes suffer from Li dendritic growth and the formation of solid electrolyte interphase (SEI), while NMC cathodes suffer from the formation of cathode electrolyte interphase (CEI) and other interface-related issues, including transition metal dissolution, oxygen release, cracking, and so on. To tackle these issues, recently, two sister techniques, atomic and molecular layer deposition (ALD and MLD), have emerged and exhibit tremendous capabilities to accurately constitute robust interfaces to achieve high-performance Li‖NMC LMBs. They can uniquely develop uniform and conformal films as surface coatings of LMBs in a precisely controllable mode at the atomic/molecular level, while proceeding with film deposition at low temperatures (e.g., ≤250 °C). In this Feature Article, we review the latest research progress in developing novel surface coatings via ALD and MLD for Li‖NMC LMBs and discuss outcomes for pursuing high performance.

25 ENERGY STORAGE↗
DOE OSTI2025

Layer-by-layer growth of graphene oxide multilayers using robust interlayer linking chemistry. 2 Zr–bissulfates

We report on the facile layer-by-layer growth of graphene oxide sulfate (GO-S) multilayer structures. The layers are bonded to a modified planar silica support using Zr 4+ ions. Optical ellipsometry shows step-by-step layer growth with layer thickness consistent with that expected from molecular mechanics calculations. The reaction to form Zr–bissulfate linkages is facile, with multistep layer deposition occurring within six to ten minutes per layer. The GO-S layers can be deposited directly on GO-S underlayer(s) or interlayer spacers can be incorporated to control the spacing with GO-S layers. X-ray photoelectron spectroscopy (XPS) data provides information on the density of the sulfonated groups present at the graphene oxide surface and on the Zr : S ratio. This is the first report we are aware of that demonstrates robust layer-by-layer growth of graphene oxide structures.

Graphene oxide↗
DOE OSTI2026

Robust photocatalytic hydrogen generation from CdSe nanoplatelets

Mercaptopropionic acid (MPA) capped-CdSe NPLs in-conjunction with a nickel-dihydrolipoic acid (Ni-DHLA) co-catalyst, yielded a robust output of photocatalytically generated hydrogen (H 2 ) at low concentrations of nanoplatelets. Furthermore, etching led to increased catalytic efficiency, suggesting that exposed catalytically active sites are primarily responsible for photocatalytic activity.

Phinney, Elizabeth O. [University of Rochester, NY↗
DOE OSTI2021

Robust hierarchical dispatch for residential distribution network management considering home thermal flexibility and model predictive control

In the transactive energy (TE) paradigm, the devices of participative consumers, or prosumers, may be aggregated and employed to drive operational objectives at the network level. Home heating, ventilation and air-conditioning (HVAC) systems in particular are well-suited to modulate their behaviours based on both home thermal flexibility and requests from the utility grid. This paper develops a robust, hierarchical power dispatch scheme in the context of a residential distribution network. The formulation couples a unique, multiphase linear distribution optimal power flow (OPF) at the upper level with model predictive control (MPC)-based HVAC fleet controllers at the lower level. The proposed approach is tested on nearly 2000 homes with a three-phase distribution network in an intraday market setting, where two major applications are explored and analysed.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2013

Kinetic effects on robustness of electron magnetohydrodynamic structures

Following recent remarkable progress in the development of high-power short-pulse lasers, exploration is ongoing into hitherto unknown phenomena at fast time scales of electrons, the understanding of which is becoming crucial. For a simplified description of such phenomena, the Electron Magnetohydrodynamics (EMHDs) fluid description is often adopted. For the possibility of electron transport in high-density plasma, exact solutions of the EMHD model in the form of electron vortex currents, together with their associated magnetic fields, have been considered. However, the fluid EMHD model does not incorporate kinetic effects. Here, the finite Larmor radius effects owing to a finite electron temperature on the robustness of the exact EMHD structures are investigated using two-dimensional particle-in-cell simulations. It is found that larger EMHD vortex structures can sustain themselves for long periods, even in high temperature plasma; however, sustaining structures at higher temperatures tends to be difficult. With increasing temperature, electrons with finite Larmor radii become disengaged from the localized region. It is also shown that structures localized in smaller regions are more difficult to sustain. A quantitative criterion in terms of the structure size and Larmor radius has been established by simulations over a wide range of parameters. Finally, we conclude that a structure, larger than about eight times the typical Larmor radius at r=R, could form and exist even under the effects of finite electron temperature.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Robustness of the filamentation instability for asymmetric plasma shells collision in arbitrarily oriented magnetic field

The filamentation instability triggered when two counter streaming plasma shells overlap appears to be the main mechanism by which collisionless shocks are generated. It has been known for long that a flow aligned magnetic field can completely suppress this instability. In a recent paper [Phys. Plasmas 18, 080706 (2011)], it was demonstrated in two dimensions that for the case of two cold, symmetric, relativistically colliding shells, such cancellation cannot occur if the field is not perfectly aligned. Here, this result is extended to the case of two asymmetric shells. The filamentation instability appears therefore as an increasingly robust mechanism to generate shocks.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Perfect and robust phase-locking of a spin transfer vortex nano-oscillator to an external microwave source

We study the synchronization of the auto-oscillation signal generated by the spin transfer driven dynamics of two coupled vortices in a spin-valve nanopillar to an external source. Phase-locking to the microwave field h{sub rf} occurs in a range larger than 10% of the oscillator frequency for drive amplitudes of only a few Oersteds. Using synchronization at the double frequency, the generation linewidth is found to decrease by more than five orders of magnitude in the phase-locked regime (down to 1 Hz, limited by the resolution bandwidth of the spectrum analyzer) in comparison to the free running regime (140 kHz). This perfect phase-locking holds for frequency detuning as large as 2 MHz, which proves its robustness. We also analyze how the free running spectral linewidth impacts the main characteristics of the synchronization regime.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Role of substrate aspect ratio on the robustness of capillary alignment

Capillary forces associated with liquid bridges formed across solid substrates are routinely exploited to align and assemble micro- and nanoscale devices. The magnitude of these forces plays a critical role in minimizing substrate misalignment and therefore should be controlled for robust and reliable fabrication process. We explore through simulations and experiments the role of the substrate aspect ratio (L/W) on capillary restoring forces and torques. Simulations show that increasing the aspect ratio of the substrates increases the capillary torques and forces when the substrates are misaligned through either lateral or rotational perturbations. The effect of substrate area, perimeter, and liquid volume are also systematically explored to show that the increase in restoring torque is caused by an increase in aspect ratio. A simple theoretical model based on the geometry of the system shows excellent agreement with Surface Evolver simulations. Finally, parameters from experimental flip-chip devices [Josell, D. Wallace, W.E. Warren, J.A. Wheeler, D. Powell, A.C. J. Electron. Packag. 124, 227, (2002)] are used in our simulations to show how current capillary self-alignment schemes could benefit from using rectangular substrate shapes with aspect ratio greater than one.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Microscopy image segmentation tool: Robust image data analysis

We present a software package called Microscopy Image Segmentation Tool (MIST). MIST is designed for analysis of microscopy images which contain large collections of small regions of interest (ROIs). Originally developed for analysis of porous anodic alumina scanning electron images, MIST capabilities have been expanded to allow use in a large variety of problems including analysis of biological tissue, inorganic and organic film grain structure, as well as nano- and meso-scopic structures. MIST provides a robust segmentation algorithm for the ROIs, includes many useful analysis capabilities, and is highly flexible allowing incorporation of specialized user developed analysis. We describe the unique advantages MIST has over existing analysis software. In addition, we present a number of diverse applications to scanning electron microscopy, atomic force microscopy, magnetic force microscopy, scanning tunneling microscopy, and fluorescent confocal laser scanning microscopy.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Trend of tunnel magnetoresistance and variation in threshold voltage for keeping data load robustness of metal–oxide–semiconductor/magnetic tunnel junction hybrid latches

The robustness of data load of metal–oxide–semiconductor/magnetic tunnel junction (MOS/MTJ) hybrid latches at power-on is examined by using Monte Carlo simulation with the variations in magnetoresistances for MTJs and in threshold voltages for MOSFETs involved in 90 nm technology node. Three differential pair type spin-transfer-torque-magnetic random access memory cells (4T2MTJ, 6T2MTJ, and 8T2MTJ) are compared for their successful data load at power-on. It is found that the 4T2MTJ cell has the largest pass area in the shmoo plot in TMR ratio (tunnel magnetoresistance ratio) and V{sub dd} in which a whole 256 kb cell array can be powered-on successfully. The minimum TMR ratio for the 4T2MTJ in 0.9 V < V{sub dd} < 1.9 V is 140%, while the 6T2MTJ and the 8T2MTJ cells require TMR ratio larger than 170%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗